Since war is technically impossible with the advent of the Global Union, IMPS are considered peacekeepers rather than a military force.
Following the introduction of the Marking program, General Lamson needed to find a way to deal with potentially subversive elements within the American Union. He found a solution by observing Chancellor Cylis's European Moderators of Peace, a secret force trained to respond in the event of an emergency. In order to deal with threats to Unity while filling the ranks of the IMPS, Lamson gave DOME orders to "flunk" any possible troublemakers who came to Pledge and transport them to IMP training centers, where they would be brainwashed and trained to serve as his private army if the need arose.
The existence of the IMPS was unknown to all except top government officials until Erin Arbitor hacked into secret files that described the mission of the Trumpet Task Force, the sole time IMPS had been used in any active capacity up to that point. When the Dust initiated the Markless protests, the IMPS were brought out of Acheron, the IMP base in Beacon City, in order to deal with the threat. IMPS were also deployed in New Chicago. Their official name has never been used in legal news releases--rather, they are merely being called "loyal men and women in uniform."
After the American Union became part of the Global Union, the IMPS were told that they would follow both Cylis and Lamson, assuming that the two men would never disagree. Cylis, however, used Champion Lily Langly (who was an Advocate at the time) to help him achieve mastery over Lamson and, thus, dominance over the IMPS.
IMPS were charged with surveillance over closed-off sectors of al-Balat, a city in the Dark Lands, in order to prevent civilians from tampering with old military equipment abandoned during the Total War. After nine-year-old Ali wandered into the old hospital, which had been a battleground, and unintentionally brought the abandoned "tinchers" to life, IMPS arrested her. Following a harsh questioning, Ali managed to escape the IMPS. Ali's eventual attack on the Global Union through the Ultranet affected the IMPS, taking down their prison security systems and allowing IMP prisoners to escape.
The IMPS have been deployed to the Dark Lands to control the Markless rebellion.
There are three IMP training locations--Acheron in Beacon City, the IMP base in New Chicago, and the Gulf Bay center in the southern American State. Sierra City is the only metropolitan center in the American State not to have an IMP base.
IMPS are divided between subservient and Controlling ranks. The lowest rank is Moderator. All IMPS enter Cylis's service at this level. The Moderators are commanded by Counselors, then Mitigators, and then Coordinators.
The lowest Controlling rank is Advocate, followed by Champion, Presider, and finally Decider. Decider is the highest possible rank, and no IMP has yet reached it.
Since IMPS enter Cylis's service as flunkees or Markless criminals, they must first Pledge their loyalty and become Marked. The Pledge, for an IMP, is seen less as an event than as a way of life. Newly arriving flunkees or Markless criminals are placed in brain-computer interface helmets that simulate torture. In order to end the simulated torture, the flunkee or Markless criminal has only to remove the helmet. The helmet, however, is outfitted with a device that will Mark the individual's forehead as he or she removes it. The nature of the helmet forces the flunkee or Markless criminal to wholeheartedly embrace Cylis's cause before removing it--in effect, brainwashing the future IMP.
The new Moderators then undergo standard military training, including weapons training. If they fail to measure up to IMP standards in some way, they are forced to undergo the Revision process. Revision means being placed into one of a different set of brain-computer interface helmets. These helmets also simulate torture, but the torture is milder than what the IMP underwent before Pledging. Any IMPS who seem to "backslide" undergo Revision, no matter their rank. Even members of Controlling ranks can be put into Revision.
The Revision process does not automatically make an IMP a good soldier. It merely makes him attempt to be a good soldier, provided the process works correctly. Problems with Revision are not common knowledge. However, some IMPS--notably, Champion Lily Langly and Moderator Eddie Blackall--have learned how to pretend submission to cause the helmet to stop the torture before Revision is complete.